1. Field of the Invention
The present invention relates to an X-ray inspection apparatus that irradiates X-rays onto an object being conveyed and detects X-rays that are transmitted therethrough in order to inspect the object.
2. Background Information
Conventionally, inspection of defective products using an X-ray inspection apparatus has been performed in production lines for food and other products in order to avoid shipment of a defective product, such as a contaminated product or a product that is split or chipped. With this type of X-ray inspection apparatus, X-rays are irradiated onto objects that are conveyed continuously by a transport conveyor, the transmitted X-rays are detected by an X-ray receiving unit, and the presence of contaminants in the inspected objects is thereby determined.
With this type of X-ray inspection apparatus, in some cases, detection of contaminants is performed by defining a mask area in order to accurately detect contaminants in a product. For example, when inspecting for the presence of a contaminant in a product placed in a container such as a can, the rim of the can appears dark in an X-ray image, and so to does the image of a contaminant. Thus, it is difficult to accurately detect the image of a contaminant that is present near the rim of the can.
Japanese Patent Publication No. 2001-281173 (published on Oct. 10, 2001) discloses an X-ray inspection apparatus that accurately detects a contaminant that is present near the rim of a can by manually defining a mask area such that the number of pixels to be removed in the arrangement direction of the line sensor will be larger than the number of pixels to be removed in the direction perpendicular thereto. In addition, Japanese Patent Publication No. S63-236989 (published on Oct. 3, 1988) discloses an X-ray inspection apparatus that performs an inspection by defining mask areas according to the container and rim, and using a different threshold for each mask area.
However, the above-described conventional X-ray inspection apparatuses have the following problems.
Specifically, with both of the X-ray inspection apparatuses disclosed in the above publications, the mask area needs to be defined manually, which can be troublesome. In addition, when the mask area is defined at a deviated position, it causes problems such that the rim of a can or the like which has a higher density in an X-ray image created based on the amount of detected X-rays, will be erroneously determined as a contaminant.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved an X-ray inspection apparatus capable of automatically defining an accurate mask area and accurately detecting contaminants that are present near the rim of a can and the like. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.